Monitoring Gaseous CO2 and Ethanol above Champagne Glasses

https://doi.org/10.1371/journal.pone.0030628

“μGC is generally employed to monitor gas of environmental interest such as CO₂, N₂O, CH₄ [36], [37]. GC coupled with a thermal conductivity detector has already been applied to the analysis of CO₂, N₂ and O₂ in beverage headspace, the respective concentration of each gas present being determined with a headspace sampler developed to puncture the beverage package (carbonated beverages or still wines) [38]. In the present study, analyses were conducted on a dual channel (A and B) micro gas chromatograph equipped with thermal conductivity detectors (TCD) (MicroGC 200, Agilent, SRA Instruments, France). On channel A, a PoraPlot U (PPU) column was set at 140°C for determination of CO₂ while analysis of ethanol was performed on channel B with a OV-1 column at 100°C. Helium was used as a carrier gas in the two columns. The injection time on both columns was 50 ms. Chromatograms were obtained every 60 s. Peaks areas were quantified using the SOPRANE software (version 2.6.5). The chromatographic conditions for the analysis of CO₂ and ethanol and the peak integration parameters used were the same as those previously described (Table S1) [39]. The quantity of CO₂ was determined by means of a calibration curve using two bottles containing respectively 10% and 1% of standard CO₂ (supplied by Linde gas, France) and air (≈0.038% of CO₂) was used as a control. Ethanol was quantified with a bottle of gas holding 0.25% of standard ethanol (supplied by Linde gas, France). Calibration with the standard bottles were made with direct connection of the bottle to the μGC sample injection valve using stainless steel tubing, avoiding any gas loss or any disturbing airstream, thus keeping constant the concentration of standard gas. The gas delivery pressure was also kept constant to 1 bar. Then, analyses and quantification of standard gases for calibration were made with the same parameters as those used for the samples (Table S1). Calibration curves plotted the relative area of CO₂ or ethanol versus the concentration of the standard. The procedure finally developed has shown a high reproducibility: 0.18% relative standard deviation (RSD) for CO₂ 10%, 0.54% RSD for CO₂ 1% and 0.28% RSD for ethanol.”